Because batteries provide power to operate a laptop computer or other portable electronic device for a limited period of time, a need exists to efficiently use the power available to provide the longest possible operating period. This need has resulted in various power saving techniques such as, for example, shutting down or reducing power in components that are not being heavily used, or where policy is to prefer power savings over performance.
One component that can have power reduced during periods of inactivity or when power conservation is preferred is the LCD panel and backlight. In a typical laptop computer, for example, the display can consume 30% or more of the power consumed by the system. In order to reduce display power consumption, some laptop computer systems reduce the panel backlighting when in battery-powered mode. However, because LCDs are transmissive display devices (i.e., LCDs depend on the quantity and quality of the backlight source for producing the perceived color gamut), reduction of backlight brightness alone results in an image that the user often perceives as of lower quality than the same image with a brighter backlighting.
Display image quality is further affected by ambient light surrounding the display, which can reduce the environments in which a user may feel comfortable using a battery powered device that adjusts the backlight to save power, which is especially important considering the self-contained battery power-source is one of the key factors facilitating mobility that allows the use to move at will between different indoor and outdoor environments.